MM-32591: Reliable Websockets: Client side changes

client/websocket_client.tsx

@@ -1,10 +1,14 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
+import {SocketEvents} from 'utils/constants';
+
 const MAX_WEBSOCKET_FAILS = 7;
 const MIN_WEBSOCKET_RETRY_TIME = 3000; // 3 sec
 const MAX_WEBSOCKET_RETRY_TIME = 300000; // 5 mins
 
+const reliableWebSockets = true;
+
 export default class WebSocketClient {
  private conn: WebSocket | null;
  private connectionUrl: string | null;
@@ -25,6 +29,7 @@ export default class WebSocketClient {
  private missedEventCallback: (() => void) | null;
  private errorCallback: ((event: Event) => void) | null;
  private closeCallback: ((connectFailCount: number) => void) | null;
+ private connectionId: string | null;
 
  constructor() {
  this.conn = null;
@@ -39,8 +44,12 @@ export default class WebSocketClient {
  this.missedEventCallback = null;
  this.errorCallback = null;
  this.closeCallback = null;
+ this.connectionId = '';
  }
 
+ // on connect, only send auth cookie and blank state.
+ // on hello, get the connectionID and store it.
+ // on reconnect, send cookie, connectionID, sequence number.
  initialize(connectionUrl = this.connectionUrl, token?: string) {
  if (this.conn) {
  return;
@@ -55,19 +64,25 @@ export default class WebSocketClient {
  console.log('websocket connecting to ' + connectionUrl); //eslint-disable-line no-console
  }
 
- this.conn = new WebSocket(connectionUrl);
+ // Add connection id, and last_sequence_number to the query param.
+ // We cannot use a cookie because it will bleed across tabs.
+ // We cannot also send it as part of the auth_challenge, because the session cookie is already sent with the request.
+ this.conn = new WebSocket(connectionUrl + '?connection_id=' + this.connectionId + '&' + 'sequence_number=' + this.serverSequence);
  this.connectionUrl = connectionUrl;
 
  this.conn.onopen = () => {
- this.serverSequence = 0;
+ // No need to reset sequence number here.
+ if (!reliableWebSockets) {
+ this.serverSequence = 0;
+ }
 
  if (token) {
  this.sendMessage('authentication_challenge', {token});
  }
 
  if (this.connectFailCount > 0) {
  console.log('websocket re-established connection'); //eslint-disable-line no-console
- if (this.reconnectCallback) {
+ if (!reliableWebSockets && this.reconnectCallback) {
  this.reconnectCallback();
  }
  } else if (this.firstConnectCallback) {
@@ -123,6 +138,9 @@ export default class WebSocketClient {
  this.conn.onmessage = (evt) => {
  const msg = JSON.parse(evt.data);
  if (msg.seq_reply) {
+ // This indicates a reply to a websocket request.
+ // We ignore sequence number validation of message responses
+ // and only focus on the purely server side event stream.
  if (msg.error) {
  console.log(msg); //eslint-disable-line no-console
  }
@@ -132,9 +150,39 @@ export default class WebSocketClient {
  Reflect.deleteProperty(this.responseCallbacks, msg.seq_reply);
  }
  } else if (this.eventCallback) {
- if (msg.seq !== this.serverSequence && this.missedEventCallback) {
- console.log('missed websocket event, act_seq=' + msg.seq + ' exp_seq=' + this.serverSequence); //eslint-disable-line no-console
- this.missedEventCallback();
+ if (reliableWebSockets) {
+ // We check the hello packet, which is always the first packet in a stream.
+ if (msg.event === SocketEvents.HELLO && this.missedEventCallback) {
+ console.log('got connection id ', msg.data.connection_id); //eslint-disable-line no-console
+ // If we already have a connectionId present, and server sends a different one,
+ // that means it's either a long timeout, or server restart, or sequence number is not found.
+ // Then we do the sync calls, and reset sequence number to 0.
+ if (this.connectionId !== '' && this.connectionId !== msg.data.connection_id) {
+ console.log('long timeout, or server restart, or sequence number is not found.'); //eslint-disable-line no-console
+ this.missedEventCallback();
+ this.serverSequence = 0;
+ }
+
+ // If it's a fresh connection, we have to set the connectionId regardless.
+ // And if it's an existing connection, setting it again is harmless, and keeps the code simple.
+ this.connectionId = msg.data.connection_id;
+ }
+
+ // Now we check for sequence number, and if it does not match,
+ // we just disconnect and reconnect.
+ if (msg.seq !== this.serverSequence) {
+ console.log('missed websocket event, act_seq=' + msg.seq + ' exp_seq=' + this.serverSequence); //eslint-disable-line no-console
+ // We are not calling this.close() because we need to auto-restart.
+ this.connectFailCount = 0;
+ this.responseSequence = 1;
+ this.conn.close(); // Will auto-reconnect after MIN_WEBSOCKET_RETRY_TIME.
+ return;
+ }
+ } else {
+ if (msg.seq !== this.serverSequence && this.missedEventCallback) {
+ console.log('missed websocket event, act_seq=' + msg.seq + ' exp_seq=' + this.serverSequence); //eslint-disable-line no-console
+ this.missedEventCallback();
+ }
  }
  this.serverSequence = msg.seq + 1;
  this.eventCallback(msg);